A. Field of the Invention
Implementations described herein relate to search engines and, more particularly, to techniques through which local search engines can efficiently retrieve documents relevant to geographical regions.
B. Description of Related Art
The World Wide Web (“web”) contains a vast amount of information. Locating a desired portion of the information, however, can be challenging. This problem is compounded because the amount of information on the web and the number of new users inexperienced at web searching are growing rapidly.
Search engines attempt to return hyperlinks to web pages in which a user is interested. Generally, search engines base their determination of the user's interest on search terms (called a search query) entered by the user. The goal of the search engine is to provide links to high quality, relevant results (e.g., web pages) to the user based on the search query. Typically, the search engine accomplishes this by matching the terms in the search query to a corpus of pre-stored web pages. Web pages that contain the user's search terms are “hits” and are returned to the user as links.
In an attempt to increase the relevancy and quality of the web pages returned to the user, a search engine may attempt to sort the list of hits so that the most relevant and/or highest quality pages are at the top of the list of hits returned to the user. For example, the search engine may assign a rank or score to each hit, where the score is designed to correspond to the relevance or importance of the web page.
Local search engines are search engines that attempt to return relevant web pages and/or business listings within a specific geographic region. For a local search, a user may enter a search query and specify a geographic region around which the search query is to be performed. The local search engine may return relevant results, such as relevant web pages pertaining to the geographic region or listings of businesses in the geographic region, to the user.
With some local search engines, the local geographic region of interest is a region defined by a certain distance or radius from a starting location, such as a certain number of miles from a zip code or street address. Ideally, the local search engine should efficiently locate and return relevant results in the desired geographic region.